A digital camera mounted on a smartphone or the like, an on-vehicle camera, and the like need to be thinner and have higher functionality. As a thinning technique of this type of digital camera, there is a technique for obtaining an object image without using a lens (for example, see PTL 1).
In this technique, a special diffraction grating substrate is attached to an image sensor, and an incident angle of incident light is obtained by an inverse problem from a projection pattern generated by light transmitted through the diffraction grating substrate on the image sensor so as to obtain an image of an object in the outside.